Best two light curves obtained during the Triton occultation of 5 October 2017, at La Palma and Helmos stations (see details in Table 1). Both telescopes were equipped with the same E2V CCD 47-20 detector with quantum efficiency peaking at 600 nm and reaching zero near 300 and 1000 nm, respectively. Left panel: full resolution light curve (cycle time 0.635 s) for the La Palma station. Right panel: same for the Helmos station (cycle time 0.674 s). The spectral ranges used for each instrument are indicated in the figures (I+z at La Palma and V+R at Helmos). The blue lines are the best simultaneous fits obtained with our ray-tracing approach (see Sect. 4).